In some nuclear reactors, feeder pipes allow heavy water to circulate to each fuel channel. Over the course of the life of the reactor, these feeder pipes may erode and/or corrode internally due to the flow accelerated corrosion under and adjacent to welds. Periodic inspections are required to determine the remaining material thickness at the weld and surrounding area for fitness-for-service assessment.
The outside surface of the inspection site offers a complex topography which includes weld crowns, curved fittings or bends, and tapered surfaces that hinders the collection of wall thickness measurements using conventional ultrasonic tools.